Traffic engineering method and node apparatus using traffic engineering method

ABSTRACT

A traffic engineering method is provided for optimizing an entire network resource, to a network divided intro a plurality of areas, each area including a plurality of nodes. According to the traffic engineering method, a load-balancing process is performed in each area separately. Thus, a memory capacity required by a node carrying out the load-balancing process can be reduced by a large amount, thereby achieving a high-speed load balancing process.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a traffic engineering method anda node apparatus using the traffic engineering method. Moreparticularly, the present invention relates to a traffic engineeringmethod and a node apparatus using the traffic engineering method in anetwork.

[0003] 2. Description of the Related Art

[0004] Recently, a great variety of information is being exchanged onthe Internet, in areas of not only data communication, but alsoreal-time services providing sounds and images. As a result, theInternet traffic has been increasing rapidly year after year. Thus, asolution is indispensable for a congestion problem on the Internet.

[0005] In a network composed of a plurality of nodes, a routing protocolthat automatically determines the most appropriate route for forwardinga packet from a source node to a destination node is, for example, anRIP (Routing Information Protocol), an OSPF (Open Shortest Path First),a BGP4 (Border Gateway Protocol Version 4), or an IS-IS (IntermediateSystem To Intermediate System). In the present network, the mostappropriate route for forwarding a packet is determined by use of theabove-described protocols, and, then, packet forwarding is carried outon the most appropriate route.

[0006]FIG. 1 is a diagram showing a related-art IP packet forwardingprocess. Generally, each node 10, 11 and 12 shown in FIG. 1 forwards apacket to a destination node by referring to a destination addressincluded in the packet.

[0007] A cut-through method has attention as a technology to forward apacket faster than the IP packet forwarding process shown in FIG. 1. Forinstance, an MPLS (Multi Protocol Label Switching) method is typical ofthe cut-through method.

[0008]FIG. 2 is a diagram showing a related-art IP packet forwardingprocess by use of the MPLS method. According to the MPLS method, an LSP(Label Switched Path) is initially set on the most appropriate routecalculated by a routing protocol, as shown in FIG. 2. Nodes located onboth ends of the LSP are called edge nodes 15 and 17. Each node, forexample, a node 16 located on the LSP between the edge nodes 15 and 17,or in an MPLS domain, is called a core node.

[0009] Next, a label is distributed to each node on the LSP fordetermining a forwarding direction, by use of an LDP (Label DistributionProtocol). An edge node on a transmitting end, that is, the edge node 15receives a packet forwarded from the outside of the MPLS domain, andadds a label L1 to the packet. Subsequently, the edge node 15 forwardsthe packet through the LSP to the core node 16. The core node 16forwards the packet received from the edge node 15 to an edge node on areceiving end, that is, the edge node 17, by referring to the label L1and switching the label L1 to a label L2.

[0010] At last, the edge node 17 receives the packet from the core node16, and deletes the label L2 from the packet. The edge node 17, then,forwards the packet to the outside of the MPLS domain. According to theMPLS method, a core node located between edge nodes only needs toforward a packet through a layer 2 by referring to a label, and, thus, afast packet forwarding process is achieved.

[0011] As described above, the fast packet forwarding is achieved by useof the routing protocol and the MPLS technology. However, if trafficincreases explosively because of an increase in the number ofsubscribers on the present Internet, network congestion or packet lossoccurs. In conclusion, the MPLS technology has a merit to enable thefast packet forwarding, but has a demerit that the network congestion orthe packet loss occurs since the MPLS technology cannot control a packetforwarding path depending on the circumstances by using software such asIP routing in a case in which the traffic is intensive.

[0012] Such network congestion and packet loss can be prevented by atraffic engineering (TE), which is a control automatically optimizingentire resources of the network. A traffic engineering function itselfdoes not depend on a layer-2 medium, but is most effectively used on thenetwork as described in the MPLS technology, setting the LSP between anode on a transmitting end and a node on a receiving end.

[0013] A load distribution system of the traffic engineering isdisclosed in Japanese Priority Application No. 12-12195, for example.The system disclosed in Japanese Priority Application No. 12-12195 setsmulti paths LSP1, LSP2 and LSP3 from a transmission node 20 to areception node 21, as shown in FIG. 3, and distributes traffic of anetwork among the multi paths LSP1, LSP2 and LSP3, thereby averagingtraffic of the entire network.

[0014] In detail, in the load distribution system, each node calculatesan average usage rate of each link connected to the node, andperiodically carries out a flooding process to all the nodes in the loaddistribution system, in order to recognize a current load on thetraffic. The transmission node 20 calculates an effective load on eachLSP based on the average usage rate of each link of all the nodesreceived by the flooding. The transmission node 20, then, moves thetraffic by each micro flow so that the effective loads on all the LSPsbecome the same value, thereby averaging the loads on the LSPs. Themicro flow is a flow used between end users. On the other hand, anaggregate flow is an aggregation of micro flows having a commondestination.

[0015] A selection of an LSP, to which a micro flow is mapped, iscarried out by use of an LSP decision table shown in FIG. 5A. Every timea new multi path is added to the load distribution system, the number ofareas separated in the LSP decision table increases. The transmissionnode 20 initially calculates a normalized value by using addressinformation included in a packet as a key. The transmission node 20,then, indexes the LSP decision table by use of the normalized value, anddecides an LSP, to which the micro flow of the packet is mapped. Thetransmission node 20 switches the LSP, to which the micro flow ismapped, by moving a boundary of the LSP in the LSP decision table asshown in FIG. 5B, in order to average the traffic of the network. Thus,the load distribution system can distribute the traffic of the networkby use of the LSP decision table.

[0016] According to the related-art traffic engineering technologydescribed above, a transmission node collects an average usage rate ofeach link transmitted periodically from all the nodes, and carries outtraffic distribution for all the LSPs together after calculating aneffective load on each LSP based on the average usage rate of each link.Therefore, the related-art traffic engineering technology enables loadbalancing in a small-size network. However, the load balancing accordingto the related-art traffic engineering technology cannot be utilized ina large-size network such as the OSPF routing protocol that includes aplurality of areas, since a load on the transmission node isconsiderably heavy.

[0017] Additionally, according to the related-art traffic engineeringtechnology, in a case in which a route is failed among a plurality ofroutes, the transmission node can only detect the failed route by usinga refresh function of the LDP or detecting a change in a networktopology. While searching for the failed route, the load distribution iscarried out among the plurality of routes including the failed route.Thus, fast relief of the traffic cannot be achieved by the related-arttraffic engineering technology. Additionally, a micro flow such as a TCP(Transmission Control Protocol) connection cannot be relieved.

SUMMARY OF THE INVENTION

[0018] Accordingly, it is a general object of the present invention toprovide a traffic engineering method and a node apparatus using thetraffic engineering method. A more particular object of the presentinvention is to provide a traffic engineering method and a nodeapparatus using the traffic engineering method, the traffic engineeringmethod carrying out a high-speed load balancing process regardless of asize of a network, and relieving a traffic loss of a failed route in acase in which a failure occurs on the network.

[0019] The above-described object of the present invention is achievedby a traffic engineering method of a network divided into a plurality ofareas, each area including a plurality of nodes, the method includingthe step of carrying out a load-balancing process in the each areaseparately.

[0020] The above-described object of the present invention is alsoachieved by a node apparatus included in a network that is divided intoa plurality of areas, each area including a plurality of nodes, in whichan entire network resource is optimized by traffic engineering, the nodeapparatus including an inside-area destination deciding unit thatdecides a destination of a packet in the each area, the destinationbeing used for carrying out a load-balancing process within the eacharea.

[0021] The node apparatus using the traffic engineering method accordingto the present invention can relieve a traffic loss speedily when afailure occurs on a path, on which the load-balancing process is beingperformed. Thus, the load-balancing process can be performed within eacharea separately, and a memory capacity required by the load-balancingnode can be reduced by a large amount even in a large-size network,thereby achieving the high-speed load balancing process.

[0022] Other objects, features and advantages of the present inventionwill become more apparent from the following detailed description whenread in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a diagram showing a related-art IP packet forwardingprocess;

[0024]FIG. 2 is a diagram showing a related-art IP packet forwardingprocess by use of an MPLS (Multi Protocol Label Switching) method;

[0025]FIG. 3 is a diagram showing a related-art traffic engineeringsystem;

[0026]FIG. 4 is a diagram showing a related-art traffic distributionsystem;

[0027]FIGS. 5A and 5B are diagrams showing LSP (Label Switched Path)decision tables used for mapping a micro flow to an LSP;

[0028]FIG. 6 is a diagram showing a structure of a network system, towhich a traffic engineering method according to the present invention isapplied;

[0029]FIG. 7 is a block diagram showing a structure of an edge node on atransmitting end, which is utilized in the traffic engineering methodaccording to the present invention;

[0030]FIG. 8 is a block diagram showing a structure of a core nodeutilized in the traffic engineering method according to the presentinvention;

[0031]FIG. 9 is a flowchart showing a default-path setting process;

[0032]FIG. 10 is a diagram showing a default path set in the networksystem;

[0033]FIG. 11 is a diagram showing collection of traffic information byuse of hardware;

[0034]FIG. 12 is a diagram showing a format of an Opaque LSA (Link-StateAdvertisement) of an OSPF (Open Shortest Path First);

[0035]FIG. 13 is a diagram showing an advertising process;

[0036]FIG. 14 is a flowchart showing a first embodiment of aload-balancing process;

[0037]FIG. 15 is a diagram showing a method of calculating a usage rateof a TE (Traffic Engineering) path group;

[0038]FIG. 16 is a diagram showing a process to monitor and decide acongestion condition;

[0039]FIG. 17 is a diagram showing a TE multi path setting process foreach area;

[0040]FIG. 18 is a flowchart showing a second embodiment of theload-balancing process;

[0041]FIG. 19 is a diagram showing a composition of adestination-address lookup table;

[0042]FIG. 20 is a diagram showing a composition of an inside-areadestination deciding table;

[0043]FIG. 21 is a diagram showing a composition of a threshold table;

[0044]FIG. 22 is a diagram showing a composition of aswitching-information deciding table;

[0045]FIGS. 23A, 23B and 23C are diagrams showing a load distributingprocess;

[0046]FIG. 24 is a diagram showing failure detection during theload-balancing process;

[0047]FIG. 25 is a flowchart showing a process carried out by a failurenotifying unit of a node detecting a failure;

[0048]FIG. 26 is a diagram showing failure notification to aload-balancing node;

[0049]FIG. 27 is a diagram showing a structure of a “Resv Tear” messageof a RSVP-LSP-Tunnel;

[0050]FIG. 28 is a diagram showing a process to store an address of theload-balancing node in each node by use of a “Path” message;

[0051]FIG. 29 is a flowchart showing a failure-notification receivingprocess carried out by the load-balancing node;

[0052]FIGS. 30A and 30B are diagrams showing a process to determinewhether a traffic loss occurs because of redistribution of traffic;

[0053]FIGS. 31A and 31B are diagrams showing a change in the thresholdtable because of the redistribution of the traffic; and

[0054]FIGS. 32A and 32B are diagrams showing load distribution afterdetecting the failure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0055] A description will now be given of preferred embodiments of thepresent invention, with reference to the accompanying drawings.

[0056]FIG. 6 is a diagram showing a structure of a network system, towhich a traffic engineering method according to the present invention isapplied.

[0057] In the network system or a network shown in FIG. 6, an OSPF (OpenShortest Path First) is used as a routing protocol. According to theOSPF, the entire network is divided into a plurality of areas, each areabeing an aggregate of a plurality of nodes. As shown in FIG. 6, thenetwork is composed of areas 25, 26 and 27. The area 25 includes nodes25 a through 25 e. The area 26 includes nodes 25 d, 25 e, and 26 athrough 26 c. Additionally, the area 27 includes nodes 26 c, and 27 athrough 27 c.

[0058] The nodes 25 a and 27 c are assumed as an ingress node and anegress node, respectively. Thus, a two-level topology structureconnected by the area 26 (a backbone area) is constructed, between thearea 25 (an ingress area) and the area 27 (an egress area). Each of thenodes 25 d, 25 e and 26 c recognizes itself as an area boundary node(ABR) by a function of the OSPF. Additionally, an MPLS (Multi ProtocolLabel Switching) is used as a cut-through method for carrying out fastswitching in the network.

[0059]FIG. 7 is a block diagram showing a structure of an edge node on atransmitting end, which is utilized in the traffic engineering methodaccording to the present invention. The ingress node 25 a shown in FIG.6 corresponds to the edge node shown in FIG. 7.

[0060] The edge node shown in FIG. 7 includes an L3 interface unit 31, abuffer unit 32, an L2 interface unit 33, a normalized-value calculatingunit (a normalizing unit) 34, a traffic distributing unit 35, anoutput-port/switching information deciding unit (a port/informationdeciding unit) 36, an L3 routing control unit 37, an inside-areadestination deciding unit (a destination deciding unit) 38, aswitching-information creating unit (an information creating unit) 39, afailure-notification receiving unit (a notification receiving unit) 40,a traffic managing unit 41, a path setting/releasing unit 43, adestination-address lookup table (an address lookup table) 44, aninside-area destination deciding table (a destination deciding table)45, threshold table 46, and a switching-information deciding table (aninformation deciding table) 47.

[0061] The L3 interface unit 31 carries out a layer-3 accepting processto an IP packet received from an external network, for instance. Thebuffer unit 32 holds packet information of a layer-3 packet received byeach node until a time to add switching information to the layer-3packet and to transmit the layer-3 packet to the next node on a route.The L2 interface unit 33 transmits the layer-3 packet reflected byinformation such as layer-3 header information that identifies a microflow, from a specified output port to the next node.

[0062] The normalized-value calculating unit 34 calculates a normalizedvalue used for carrying out a load-balancing process, from the packetinformation, based on characteristics of actual traffic such as a sourceaddress and a destination address. The traffic distributing unit 35decides which route in a traffic engineering (TE) path group the trafficis assigned to, based on the normalized value calculated by thenormalized-value calculating unit 34. Additionally, in a case in which afailure occurs on a route, the traffic distributing unit 35 is notifiedof a result of determining whether a traffic loss occurs because ofcarrying out the load-balancing process by use of all the routes excepta failed route. If it is recognized that the traffic loss does notoccur, the traffic distributing unit 35 redistributes the trafficflowing through the failed route, to the other plurality of routes. Onthe other hand, if it is recognized that the traffic loss occurs, thetraffic distributing unit 35 sets a new route, and switches the trafficflowing through the failed route, to the new route. Subsequently, thetraffic distributing unit 35 carries out the load-balancing process.

[0063] The output-port/switching-information deciding unit 36 decides apacket output port corresponding to a specified destination and aspecified path, and decides every parameter necessary for creating theswitching information, at each node. The L3 routing control unit 37searches for routing information of its own node from the destinationaddress, and selects a route to a destination node, to which theload-balancing process is carried out. The inside-area destinationdeciding unit 38 decides a destination inside an area instead of adestination in the entire network, which is necessary for carrying outthe load-balancing process.

[0064] The switching-information creating unit 39 creates the switchinginformation to be forwarded to the next node, and adds the normalizedvalue calculated based on the source address and the destinationaddress, to the switching information. The failure-notificationreceiving unit 40 receives a failure notification from a failuredetecting node, and determines whether the traffic loss occurs becauseof carrying out the load-balancing process by use of all the routesexcept the failed route. The traffic managing unit 41 holds trafficinformation notified from all the nodes in the area. The pathsetting/releasing unit 43 sets or deletes a path composing the TE pathgroup.

[0065] The destination-address lookup table 44 is a search table usedfor obtaining destination-node information from the destination address.The inside-area destination deciding table 45 is a search table used fordeciding which destination range in the area the load-balancing processis carried out, based on the destination-node information. The thresholdtable 46 is a search table used for obtaining destinations of thetraffic to be redistributed (the TE path group and the LSPs) in order tocarry out the load-balancing process in the area. Theswitching-information deciding table 47 is a search table used forobtaining an output destination of the packet and the switchinginformation, based on information related to the destination inside thearea and destinations of the traffic to be redistributed.

[0066] The inside-area destination deciding unit 38 and thefailure-notification receiving unit 40 are newly added to the edge node,according to the present invention. Additionally, the inside-areadestination deciding table 45 is added as necessary data to the edgenode. Further, the traffic distributing unit 35 and theswitching-information creating unit 39 includes additional functions,according to the present invention.

[0067] A description will now be given of a process carried out by theingress node 25 a. The L3 interface unit 31 initially receives a layer-3packet from an external network such as a company or an ISP (InternetService Provider), and supplies address information included in thepacket to the normalized-value calculating unit 34 and the L3 routingcontrol unit 37. Subsequently, the buffer unit 32 stores the packetinformation.

[0068] After receiving the address information from the L3 interfaceunit 31, the L3 routing control unit 37 specifies a destination nodelocated at the end of a path by searching through thedestination-address lookup table 44 by use of a destination address, andsupplies destination-node information to the inside-area destinationdeciding unit 38. A transmission node (an ingress node) according to therelated-art traffic engineering method carries out the load-balancingprocess in a range from the transmission node to the destination node.On the other hand, the ingress node 25 a according to the presentinvention carries out the load-balancing process by each area. Thus, theinside-area destination deciding unit 38 decides a destination, that is,an area boundary node, inside an area including the ingress node 25 a,by searching through the inside-area destination deciding table 45 byuse of the destination-node information obtained by the L3 routingcontrol unit 37. Subsequently, the inside-area destination deciding unit38 notifies the output-port/switching-information deciding unit 36 andthe traffic distributing unit 35 about the destination inside the area.

[0069] On the other hand, the normalized-value calculating unit 34,after receiving the address information from the L3 interface unit 31,calculates a normalized value used for carrying out the load-balancingprocess by applying a normalization function to the address information,and supplies the normalized value to the traffic distributing unit 35and the switching-information creating unit 39.

[0070] The traffic distributing unit 35 decides which route in the TEpath group the traffic is assigned to, by referring to the thresholdtable 46 based on the destination inside the area obtained by theinside-area destination deciding unit 38, and the normalized valuecalculated by the normalized-value calculating unit 34. Subsequently,the traffic distributing unit 35 notifies theoutput-port/switching-information deciding unit 36 about the result ofdeciding which route in the TE path group the traffic is assigned to.Additionally, the traffic managing unit 41 receives traffic informationnotified periodically from all the nodes in the area through the L2interface unit 33, and supplies the traffic information to the trafficdistributing unit 35.

[0071] The output-port/switching information deciding unit 36 searchesthrough the switching-information deciding table 47 by use of theinformation received from the traffic distributing unit 35 and theinside-area destination deciding unit 38, and decides an output portused for forwarding the packet to the next node, and switchinginformation to be set in the packet. Subsequently, theoutput-port/switching-information deciding unit 36 notifies theswitching-information creating unit 39 about the output port and theswitching information.

[0072] According to the related-art traffic engineering method, theswitching-information creating unit 39 creates the switching informationto the next node based on the information supplied from theoutput-port/switching-information deciding unit 36, and supplies thecreated switching information to the L2 interface unit 33. On the otherhand, the switching-information creating unit 39 according to thepresent invention adds the normalized value calculated by thenormalized-value calculating unit 34 to the switching information, andsupplies the switching information to the L2 interface unit 33. The L2interface unit 33, after receiving the switching information from theswitching-information creating unit 39, reflects the contents of theswitching information to the packet stored in the buffer unit 32, andtransmits the packet from the output port to the next node.

[0073]FIG. 8 is a block diagram showing a structure of a core nodeutilized in the traffic engineering method according to the presentinvention. The core node shown in FIG. 8 corresponds to the nodes 25 b,25 c, 25 d and 25 e of the area 25, the nodes 26 a, 26 b and 26 c of thearea 26, and the nodes 27 a, 27 b and 27 c of the area 27.

[0074] The core node shown in FIG. 8 includes an L2 interface unit 51(upstream), a buffer unit 52, an L2 interface unit 53 (downstream), anormalized-value extracting unit (an extracting unit) 54, a trafficdistributing unit 55, an output-port/switching-information deciding unit(a port/information deciding unit) 56, an L2 routing control unit 57, aninside-area destination deciding unit (a destination deciding unit) 58,a switching-information creating unit (an information creating unit) 59,a failure-notification receiving unit (a notification receiving unit)60, a traffic managing unit 61, a failure notifying unit 62, a pathsetting/releasing unit 63, a destination-address lookup table (anaddress lookup table) 64, an inside-area destination deciding table (adestination deciding table) 65, a threshold table 66 and aswitching-information deciding table (an information deciding table) 67.

[0075] The L2 interface unit 51 carries out a process to receive apacket transmitted from a node on an upstream side of the traffic.Additionally, if the core node detects a failure on a route, the L2interface unit 51 transmits a failure notification to the closest nodethat carries out the load-balancing process. The buffer unit 52 holds apacket received by each node until a time to transmit the packet to thenext node after editing switching information. The L2 interface unit 53transmits the packet reflected by the switching information on thedownstream side, from a specified output port to the next node.

[0076] The normalized-value extracting unit 54 extracts anormalized-value used for carrying out the load-balancing process fromthe switching information. The traffic distributing unit 55 decideswhich route in the TE path group the traffic is assigned to, byfollowing the normalized value extracted by the normalized-valueextracting unit 54. Additionally, in a case in which a failure occurs ona route, the traffic distributing unit 55 is notified of a result ofdetermining whether a traffic loss occurs because of carrying out theload-balancing process by use of all the routes except a failed route.If it is recognized that the traffic loss does not occur, the trafficdistributing unit 55 redistributes the traffic flowing through thefailed route, to the other plurality of routes. On the other hand, if itis recognized that the traffic loss occurs, the traffic distributingunit 55 sets a new route, and switches the traffic flowing through thefailed route, to the new route. Subsequently, the traffic distributingunit 55 carries out the load-balancing process.

[0077] The output-port/switching-information deciding unit 56 decides apacket output port corresponding to a specified destination and aspecified path, and decides every parameter necessary for creating theswitching information, at each node. The L2 routing control unit 57searches for routing information of its own node from the destinationaddress, and selects a route to a destination node, to which theload-balancing process is carried out. The inside-area destinationdeciding unit 58 decides a destination inside an area instead of adestination in the entire network, which is necessary for carrying outthe load-balancing process.

[0078] The switching-information creating unit 59 creates the switchinginformation to be forwarded to the next node, and adds the normalizedvalue calculated based on the source address and the destinationaddress, to the switching information. The failure-notificationreceiving unit 60 receives a failure notification from the failuredetecting node, and determines whether the traffic loss occurs becauseof carrying out the load-balancing process by use of all the routesexcept the failed route. The traffic managing unit 61 holds trafficinformation notified from all the nodes in the area. In a case in whicha failure occurs on a route, the failure notifying unit 62 notifies theclosest node on the upstream carrying out the load-balancing processfrom the node having detected the failure. The path setting/releasingunit 63 sets or deletes a path composing the TE path group.

[0079] The destination-address lookup table 64 is a search table usedfor obtaining destination-node information from the destination address.The inside-area destination deciding table 65 is a search table used fordeciding which destination range in the area the load-balancing processis carried out based on the destination-node information. The thresholdtable 66 is a search table used for obtaining destinations of thetraffic to be redistributed (the TE path group and the LSPs) in order tocarry out the load-balancing process in the area. Theswitching-information deciding table 67 is a search table used forobtaining an output destination of the packet and the switchinginformation, based on information related to the destination inside thearea and destinations of the traffic to be redistributed.

[0080] The newly added units according to the present invention are thenormalized-value extracting unit 54, the inside-area destinationdeciding unit 58, the failure-notification receiving unit 60 and thefailure notifying unit 62. Additionally, the inside-area destinationdeciding table 65 is also added as necessary data to the core node.Additionally, the traffic distributing unit 55 includes additionalfunctions according to the present invention. The edge node and the corenode are described separately. However, a function of each of the edgenode and the core node can be achieved by setting differently in a sameapparatus.

[0081] A description will now be given of a process carried out by thecore node. The core node initially receives a packet transmitted fromthe previous node on the upstream side by use of the L2 interface unit51. The L2 interface unit 51, then, supplies switching informationincluded in the packet to the normalized-value extracting unit 54 andthe L2 routing control unit 57. Subsequently, the buffer unit 52 storesthe packet information.

[0082] If the core node is set to a node carrying out the load-balancingprocess, and is an area boundary node on a path, the L2 routing controlunit 57 included in the core node specifies a destination node locatedat the end of the path, by searching through the destination-addresslookup table 64, based on the switching information supplied from the L2interface unit 51. Subsequently, the L2 routing control unit 57 notifiesthe inside-area destination deciding unit 58 about destination-nodeinformation.

[0083] Similarly to the above-described edge node, the inside-areadestination deciding unit 58 decides a destination, that is, an areaboundary node or a destination node, inside an area including the corenode, by searching through the inside-area destination deciding table 65based on the destination-node information obtained by the L2 routingcontrol unit 57. Subsequently, the inside-area destination deciding unit58 notifies the output-port/switching information deciding unit 56 andthe traffic distributing unit 55 about the destination inside the area.

[0084] According to the related-art traffic engineering method, only theingress node needs to obtain the normalized value used for theload-balancing process. On the other hand, according to the presentinvention, the load-balancing process is performed inside each area.Thus, the normalized-value extracting unit 54 of the core node shown inFIG. 8 extracts the normalized value necessary for carrying out theload-balancing process inside the area including the core node, andsupplies the normalized value to the traffic distributing unit 55.

[0085] The traffic distributing unit 55 decides which route in the TEpath group the traffic is assigned to, by referring to the thresholdtable 66 based on the destination inside the area obtained by theinside-area destination deciding unit 58, and the normalized valuecalculated by the normalized-value calculating unit 54. Subsequently,the traffic distributing unit 55 notifies theoutput-port/switching-information deciding unit 56 about the result ofdeciding which route in the TE path group the traffic is assigned to.Additionally, the traffic managing unit 61 receives traffic informationnotified periodically from all the nodes in the area including the corenode through the L2 interface unit 53, and supplies the trafficinformation to the traffic distributing unit 55.

[0086] In a case in which the core node is not a node carrying out theload-balancing process in the area, the normalize-value calculating unit54 and the traffic distributing unit 55 do not need to carry out theabove-described processes. The output-port/switching-informationdeciding unit 56, the switching-information creating unit 59 and the L2interface unit 53 operate similarly to theoutput-port/switching-information deciding unit 36, theswitching-information creating unit 39 and the L2 interface unit 33included in the previously-described edge node. The destination node 27c is not directly related to the load-balancing process, and, thus, adescription of the destination node 27 c will be omitted. Additionally,the node carrying out the load-balancing process is defined as an areaboundary node carrying out the load-balancing process among the corenodes in an area. If the area boundary node is not located on an LSP,the area boundary node does not carry out the load-balancing process.

[0087] According to the above-described core node, the load-balancingprocess can be carried out inside in each area of a large-size network.Thus, the most appropriate traffic engineering can be performed even ifthe size of the network is large. Additionally, the load-balancingprocess can be performed during the fast packet forwarding process withadvantages of the cut-through packet forwarding method, by inserting thenormalized value calculated by the edge node to a packet, and bytransmitting the packet to the area boundary node.

[0088] A description will now be given of a process carried out by theedge node located on the upstream side to handle a failure occurred on aroute.

[0089] When the failure occurs on a route, the failure-notificationreceiving unit 40 of the edge node receives a failure notificationtransmitted from a core node having detected the failure, through the L2interface unit 33 of the edge node. Subsequently, thefailure-notification receiving unit 40 determines whether the trafficloss occurs in the case of redistributing the traffic flowing throughthe failed route, to a plurality of routes other than the failed route,based on the traffic information notified from each node. Thefailure-notification receiving unit 40, then, notifies the result of theabove-described determination to the traffic distributing unit 35.

[0090] If the traffic distributing unit 35 is notified from thefailure-notification receiving unit 40 that the traffic loss does notoccur, the traffic distributing unit 35 redistributes the trafficflowing through the failed route, to the plurality of routes other thanthe failed route. On the other hand, if the traffic distributing unit 35is notified from the failure-notification receiving unit 40 that thetraffic loss occurs, the traffic distributing unit 35 adds a new routedifferent from the failed route, and switches the traffic flowingthrough the failed route, to the new route, thereby carrying out theload-balancing process.

[0091] A description will now be given of a process carried out by acore node in an area to handle a failure occurred on a route.

[0092] When the failure occurs on a route, on which the load-balancingprocess is performed, the failure notifying unit 62 of the core nodereceives a notification about the failure from the L2 interface unit 53,and transmits a failure notification from the L2 interface unit 51 tothe closest node carrying out the load-balancing process, that is eitherthe ingress node or an area boundary node on a packet forwarding path inthe area.

[0093] On the other hand, if the core node is the node that carries outthe load-balancing process in the area, the core node carries out thesame process as the edge node if receiving the failure notification froma node having detected the failure. As described above, the node havingdetected the failure notifies the node carrying out the load-balancingprocess. The node carrying out the load-balancing process, then,redistributes the traffic flowing through the failed route, to theplurality of routes other than the failed route. Therefore, the trafficengineering method according to the present invention can achieve fastrelief of the traffic loss.

[0094] Additionally, if the node carrying out the load-balancing processdetermines that the traffic loss occurs by redistributing the trafficflowing through the failed route, to the route other than the failedroute, the node sets a new route, and switches the traffic flowingthrough the failed route, to the new route. Accordingly, the trafficflowing through the failed route can be relieved.

[0095] A description will be further given of detailed embodiments ofthe present invention.

[0096] A default LSP (Label Switched path) is initially set, based onthe most appropriate route calculated by the OSPF. Several methods suchas an LDP (Label Distribution Protocol) and a RSVP-LSP-Tunnel (an MPLSextended version of the RSVP) are suggested as protocols used forsetting an LSP. A default-path setting process is shown in FIG. 9 for acase of using the RSVP-LSP-tunnel.

[0097] At a step S10 shown in FIG. 9, the path setting/releasing unit 43of the edge node shown in FIG. 7 or the path setting/releasing unit 63of the core node shown in FIG. 8 calculates the most appropriate routebetween the edge nodes 25 a and 27 c by use of the OSPF, afterrecognizing a path-setting request. Subsequently, at a step S12, theingress node 25 a transmits a “Path” message that follows the mostappropriate route calculated by the path setting/releasing unit 43 or63, from the L2 interface unit 33 or 55 to the destination (egress) node27 c, as shown in FIG. 10. In response, the destination node 27 ctransmits a reception message (a “Resv” message) on the reverse route tothe ingress node 25 a. When the ingress node 25 a receives the Resvmessage from the destination node 27 c, a default path (a default LSP)is set for packet forwarding.

[0098] After the traffic starts flowing through the default path, eachof the nodes 25 a, 25 b, 25 d, 26 a, 26 c, 27 a and 27 c periodicallycollects the number of transmitted packets and the number of discardedpackets as statistical information for each physical link (each physicalchannel) of an output port, by use of hardware, as shown in FIG. 11.Additionally, each of the nodes calculates a usage rate of each physicallink based on the number of transmitted packets and the number ofdiscarded packets, and adds the usage rate of each physical link to thestatistical information, in order to recognize a current load conditionof the traffic at each of the nodes.

[0099] Each node notifies all the other nodes in the area including theeach node about the statistical information including an average usagerate for each physical link, by use of an Opaque LSA (Link-StateAdvertisement) of the OSPF. The Opaque LSA is an LSA extended for a userto use the LSA depending on a general purpose, the LSA being included ina packet of an OSPF message used for exchanging a situation between eachnode by use of the OSPF message. FIG. 12 is a diagram showing a formatof the Opaque LSA of the OSPF. According to the Opaque LSA, thestatistical information is stored for the number of cards, after an OSPFpacket header and an Opaque LSA header.

[0100]FIG. 13 is a diagram showing an advertising process. An area #10shown in FIG. 13 includes nodes A, B, C and D. The node A advertises theOpaque LSA to all the adjacent nodes B, C and D. Similarly, each of thenodes B, C and D advertises the Opaque LSA received from the node A toall of its adjacent nodes. However, if a node having received the OpaqueLSA receives the same Opaque LSA again, the node discards the Opaque LSAreceived at the second time. Consequently, advertisement information iscreated.

[0101] According to the related-art traffic engineering method, only theingress node collects such advertisement information, and manages theadvertisement information. However, according to the present invention,a node recognizing itself as an area boundary node on the LSP needs tocarry out the load-balancing process in addition to the ingress node.Thus, the traffic managing unit 41 (61) of the ingress node and the areaboundary node collects the advertisement information, and manages theadvertisement information.

[0102] A description will now be given of a process carried out by aload-balancing node that is a node carrying out the load-balancingprocess. FIG. 14 is a flowchart showing a first embodiment of theload-balancing process.

[0103] A node included in an area periodically collects the trafficinformation about all the nodes included in the area by the floodingprocess. At a step S20, it is determined whether the node is aload-balancing node. Only if it is determined at the step S20 that thenode is the load-balancing node, the node proceeds to a step S22. At thestep S22, the traffic distributing unit 35 (55) of the load-balancingnode obtains the average usage rate of each link connected to each nodein the area, from the traffic managing unit 41 (61) that has receivedthe average usage rate by the advertising process, and calculatestraffic of a TE (Traffic Engineering) path group.

[0104] The TE path group is a group of paths including the default pathset by the default-path setting process and all the TE multi paths ofthe default path. A method of calculating the usage rate of the TE pathgroup is shown in FIG. 15, for example. If a label switched path LSP1 isset as the default path including a plurality of links (LINK 1, 2, . . ., i, . . . , n) as shown in FIG. 15, an effective load on the LSP1 iscalculated based on the traffic information of each link obtained by theadvertising process. Subsequently, the usage rate of the TE path groupincluding LSPs (LSP 1, . . . , i, . . . , n) is calculated, based on theeffective load on each LSP.

[0105] At a step S24 shown in FIG. 14, the 25 traffic distributing unit35 (55) of the load-balancing node calculates the usage rate of the TEpath group periodically, as shown in FIG. 16. If the usage rate of theTE path group exceeds an upper threshold continuously for a certainperiod, the traffic distributing unit 35 (55) determines that thedefault path is congested, and directs the path setting/releasing unit43 (63) to add a new TE multi path, at a step S26 shown in FIG. 14.

[0106] In the related-art traffic engineering method, a range of settinga TE multi path is same as a range of setting the default path from theingress node to the egress (the destination node). On the other hand, arange of setting the TE multi path according to the present invention islimited inside each area 25, 26 and 27, as shown in FIG. 17. It shouldbe noted that a solid line, a chained line and a broken line shown inFIG. 17 are respectively an LSP set as the default path, an LSP set asan existing multi path, and an LSP added as a new multi TE path.Additionally, the nodes 25 a, 25 d and 26 c are the load-balancingnodes.

[0107] Each of the load-balancing nodes 25 a, 25 d and 26 c repeats theabove-described processes, in accordance with a congestion situation.Every time it is determined that the TE path group is congested becauseof increased traffic, each load-balancing node adds a new TE multi path.On the other hand, if the usage rate (the traffic) of the TE path groupis less than a lower threshold, each load-balancing node determines thatthe congestion is released, and deletes the newly added TE multi path,at a step S28 shown in FIG. 14.

[0108] A description will now be given of a second embodiment of theload-balancing process, with reference to a flowchart shown in FIG. 18.This load-balancing process is performed when the ingress node 25 areceives a packet from the outside of the MPLS domain through its L3interface unit 31.

[0109] At a step S30 shown in FIG. 18, a node decides whether the nodeis the ingress node. If it is determined at the step S30 that the nodeis the ingress node, the node proceeds to a step S32. At the step S32,the L3 routing control unit 37 of the node searches through thedestination-address lookup table 44 shown in FIG. 19, by use of adestination address extracted from the packet, thereby determining anassociate pointer corresponding to the destination node located at theend of the packet forwarding path. Subsequently, the inside-areadestination deciding unit 38 searches through the inside-areadestination deciding table 45 shown in FIG. 20 by use of the associatepointer, and determines a load-balancing table pointer (an L. B. tablepointer) corresponding to a load-balancing destination. Theload-balancing destination is not a destination to the destination node,but is a destination, which is used for carrying out the load-balancingprocess in an area. Subsequently, at a step S34, the normalized-valuecalculating unit 34 calculates a normalized value (0-65535) based on anIP source address and an IP destination address included in the packet,by using a hash function (CRC16), and proceeds to a step S42.

[0110] On the other hand, if it is determined at the step S30 that thenode is not the ingress node, the node proceeds to a step S36, anddecides whether the node is a load-balancing node. If it is determinedat the step S36 that the node is the load-balancing node, the node isalso an area boundary node, and proceeds to a step S38. At the step S38,the L2 routing control unit 57 searches through the destination-addresslookup table 64 based on a value of a label added to the packet by theMPLS, and obtains the associate pointer. The searching speed may beincreased by use of hardware having a special memory such as a CAM.Subsequently, the inside-area destination deciding unit 58 searchesthrough the inside-area destination deciding table 65, and decides theload-balancing table pointer corresponding to the load-balancingdestination. At a step S40, the normalized-value extracting unit 54,then, extracts the normalized value added to switching information, andproceeds to the step S42.

[0111] At the step S42, the traffic distributing unit 35 (55) searchesfor an area through the threshold table 46 (66) shown in FIG. 21, by useof the load-balancing table pointer. The area corresponding to theload-balancing table pointer in the threshold table 46 (66) includes aplurality of thresholds indicating what ratio the load-balancing processshould be performed for each LSP included in the TE path group. Forexample, in a case in which the TE path group including a single defaultpath and two TE multi paths carries out the load-balancing process, thearea of the threshold table 46 (66) that stores the plurality ofthresholds is divided into three areas by two load-distributing boundaryvalues, each area corresponding to one of the paths LSP1, LSP2 and LSP3,as shown in FIG. 23A.

[0112] A total area of the three areas corresponding to the paths LSP1,LSP2 and LSP3 in the threshold table 46 (66) is assigned in a range ofthe normalized value (0-65535), and, thus, the traffic distributing unit35 (55) can determine which LSP in the TE path group the traffic isdistributed to, by comparing the normalized value with areas inside thethreshold table 46 (66). Additionally, every time a TE multi path isadded to the TE path group at the step S26 shown in FIG. 14, or everytime the TE multi path is removed from the TE path group at the step S28shown in FIG. 14, the number of the load-distributing boundary valuesincreases or decreases in the area corresponding to the TE path group inthe threshold table 46 (66). Thus, the load-distributing boundary valuesare set again in the area.

[0113] At a step S44, the output-port/switching-information decidingunit 36 (56) receives the load-balancing destination in the area, fromthe inside-area destination deciding unit 38 (58), and information aboutwhich LSP the traffic is distributed to, from the traffic distributingunit 35 (55). Additionally, the output-port/switching-informationdeciding unit 36 (56) searches through the switching-informationdeciding table 47 (67) shown in FIG. 22, based on the load-balancingdestination and the information received respectively from theinside-area destination deciding unit 38 (58) and the trafficdistributing unit 35 (55), and, then, obtains label information to beadded to the packet when outputting the packet to the next node, and anoutput port through which the packet is outputted.

[0114] At a step S45, the node decides whether the node is the ingressnode. According to the present invention, only if it is determined atthe step S45 that the node is the ingress node, the node proceeds to thestep S46, and adds the normalized value calculated by the hash functionto the switching information created by the switching-informationcreating unit 39 (59), as shown in FIG. 23B. Then, the switchinginformation is outputted to the next node.

[0115] According to the step S46, the ingress node adds the normalizedvalue to the switching information included in the packet, and transmitsthe packet to the next node on the packet forwarding path. Since an areaboundary node on the packet forwarding path also carries out theload-balancing process similarly to the ingress node, thenormalized-value extracting unit 54 of the area boundary node havingreceived the packet refers to the normalize value added by the ingressnode to the switching information included in the packet, as shown inFIG. 23C. Accordingly, the area boundary node can carry out a loaddistributing process similarly to the ingress node. In other words, in acase in which a load-balancing node is an area boundary node, theload-balancing node does not need to calculate a normalized value from adestination address, just by using the normalized value calculated bythe ingress node, thereby achieving a fast packet forwarding.

[0116] A description will now be given of a situation in which a failureoccurs on a path, provided that the load-balancing process is beingperformed on a plurality of paths as described above.

[0117] If a link failure or a node failure occurs on a multi path, onwhich the load-balancing process is being carried out, such failure isdetected by recognizing a change in a topology by use of, for instance,a Hello protocol of the OSPF exchanged between adjacent nodes in acomparatively long default thirty-seconds cycle, according to therelated-art traffic engineering method. On the other hand, according tothe present invention, the failure is recognized earlier than therelated-art traffic engineering method, by carrying out failurenotification triggered by detection of an LOS (Loss Of Signal) or an LOF(Loss Of Frame) of each link, as an existing hardware function. In FIG.24, the core node 26 a recognizes the failure.

[0118]FIG. 25 is a flowchart showing a process carried out by thefailure notifying unit 62 of a node having detected a failure. At a stepS50 shown in FIG. 25, the failure notifying unit 62 of the node decideswhether the node is a load-balancing node. If it is determined at thestep S50 that the node is the load-balancing node, the failure notifyingunit 62 does not need to notify about the failure, and, thus, the nodecarries out a later-described failure-notification receiving process, ata step S52. On the other hand, if it is determined at the step S50 thatthe node is not the load-balancing node, the failure notifying unit 62of the node notifies the closest load-balancing node on the upstreamside of the packet forwarding path, that is, the ingress node or an areaboundary node, about the failure, at a step S54. For instance, the corenode 26 a having detected the failure notifies the area boundary node 25d about the failure, as shown in FIG. 26.

[0119] The load-balancing node can be notified of the failure, forinstance, by transmitting a “Resv Tear” message of the RSVP-LSP-Tunnelshown in FIG. 27, from the L2 interface unit 51 of the node havingdetected the failure to the load-balancing node. Alternatively, theload-balancing node can be notified of the failure by a failurenotifying method using hop-by-hop for each link, or by setting an LSPused for notifying the failure on a direction opposite of the traffic.In the case of using the Resv Tear message, an address of theload-balancing node is set inside a SESSION object of a “Path” messagetransmitted for setting a packet forwarding path, for example. Theaddress of the load-balancing node included in the Path message isreplaced in order, every time the Path message passes through theload-balancing node, as shown in FIG. 28. Each node on the packetforwarding path stores the address of the load-balancing node thereinwhen the Path message passes through the each node. Accordingly, when anode detects a failure on the packet forwarding path, the node cannotify the load-balancing node about the failure, by transmitting theResv Tear message to the address of the load-balancing node stored inthe node.

[0120]FIG. 29 is a flowchart showing the failure-notification receivingprocess carried out by the load-balancing node. A node initiallyreceives a failure notification from a node located on the downstreamside in an area. At a step S60 shown in FIG. 29, the node decideswhether the node is a load-balancing node. If it is determined at thestep S60 that the node is not the load-balancing node, the node forwardsthe failure notification to a node located on the upstream side on thepacket forwarding path. On the other hand, if it is determined at thestep S60 that the node is the load-balancing node, the node proceeds toa step S62. At the step S62, the failure-notification receiving unit 40(60) of the node determines whether the traffic flowing through thefailed route can be redistributed to all the routes other than thefailed route, by using a usage rate of each LSP collected during theload-balancing process.

[0121] For example, a TE path group shown in FIG. 30A includes the pathsLSP1, LSP2 and LSP3. The bandwidths of the paths LSP1, LSP2 and LSP3 arerespectively 10 Mbps, 30 Mbps and 10 Mbps. Currently, 6 Mbps of the pathLSP1, 25 Mbps of the path LSP2 and 4 Mbps of the path LSP3 are used.Now, it is assumed that a failure occurs on the path LSP1 during theload-balancing process using usage rates shown in FIG. 30A. In such acase, an effective load (6 Mbps) on the path LSP1 is compared with aresult of subtracting an available bandwidth (4 Mbps) of the path LSP1from an available bandwidth (15 Mbps) of the entire TE path group. Theresult is larger than the effective load on the failed path LSP1. Thus,it is determined at the step S62 that a traffic loss does not occur byredistributing the traffic to flowing through the failed path LSP1, tothe other paths LSP2 and LSP3. Subsequently, at a step S64, the trafficdistributing unit 35 (55) redistributes the traffic to the paths LSP2and LSP3. Meanwhile, the number of the load-distributing boundary valuesis decreased by one in the threshold table 46 (66), as shown in FIG.31A, since an area corresponding to the path LSP1 is deleted. The areais, then, redistributed among the paths LSP2 and LSP3. This loaddistribution is shown in FIG. 32A.

[0122] On the other hand, if it is determined at the step S62 that thetraffic loss occurs by redistributing the traffic to the paths LSP2 andLSP2 as shown in FIG. 30B, the traffic distributing unit 35 (55) directsthe path setting/releasing unit 43 (63) to add a new TE multi path LSP4inside an area including the paths LSP2 and LSP3, at a step S66. Amethod of adding a new TE multi path is the same as the process to add anew TE multi path in the load-balancing process. After the new TE multipath LSP4 is added to the TE path group, the traffic distributing unit35 (55) switches the traffic flowing through the failed path LSP1, tothe new TE multi path LSP4, at a step S68. Meanwhile, the areacorresponding to this TE path group is changed, as shown in FIG. 31B.Additionally, the above-described process is also shown in FIG. 32B.

[0123] By taking the above-described processes, a node apparatus usingthe traffic engineering method according to the present invention canrelieve a traffic loss speedily when a failure occurs on a path, onwhich the load-balancing process is being performed. For example, in acase in which a failure occurs on a route during a service such as aTelnet using the TCP between users through an OSPF network, a connectionbetween the users is possibly cut since the users cannot receive an“Ack” message normally until the failure is detected and fixed. On theother hand, the disconnection can be avoided by performing a high-speedfailure detection and traffic relief, according to the presentinvention.

[0124] Additionally, by carrying out the load-balancing process in eachclosed area in a large-size routing protocol network using a concept ofhierarchy such as areas of the OSPF, each node in the area only needs tohold all the traffic data (information) in the area, and does not needto hold data of all the areas used for the traffic engineering.Therefore, a memory capacity required by the load-balancing node can bereduced by a large amount, and the most appropriate traffic engineeringcan be achieved in the large-size network, whereas the trafficengineering cannot be achieved by an existing technology.

[0125] Additionally, an edge node calculates a normalized value used forthe load-balancing process, based on a source address and a destinationaddress, and supplies the normalized value to an area boundary node,which carries out the load-balancing process by using the normalizedvalue. Thus, the area boundary node does not need to identify protocolssuch as an IP protocol and an IPX protocol, and to check a header of theIP protocol or the like, thereby enabling the load-balancing process inthe fast forwarding while taking advantages of the cut-through packetforwarding method.

[0126] Additionally, in a case in which a failure occurs on a routewhile carrying out the load-balancing process by use of a plurality ofroutes, a node detecting the failure notifies the load-balancing nodeabout the failure. Subsequently, the load-balancing node distributes thetraffic flowing through the failed route, to the plurality of routesother than the failed route, thereby enabling the fast relief of thetraffic loss caused by the traffic flowing through the failed route. Inthe related-art technology, a connection needs to be rebuilt inaccordance with a user trigger after a change occurs. On the other hand,according to the present invention, the traffic loss can be relievedspeedily, and, thus, aggregated micro flows of a TCP connection or thelike can be relieved.

[0127] Further, if the load-balancing node having received a failurenotification determines that the traffic loss occurs by distributing thetraffic flowing through the failed route, to the plurality of routesother than the failed route, the load-balancing node sets a new route,and switches the traffic flowing through the failed route, to the newroute. Accordingly, the present invention can provide a highly reliableconnectionless packet forwarding service, which can relieve the trafficflowing through the failed route even if routes other than the failedroute have high traffic.

[0128] According to the present invention, the load-balancing process isperformed in each area separately. In detail, a node apparatus in anarea has an inside-area destination deciding unit used for deciding adestination of a packet in the area, in order to carry out theload-balancing process within the area. Thus, the load-balancing processcan be performed within each area separately, and a memory capacityrequired by the load-balancing node is reduced by a large amount even ina large-size network, thereby achieving the high-speed load-balancingprocess.

[0129] Additionally, a node apparatus corresponding to an ingress nodesupplied with a packet from the outside has a normalized-valuecalculating unit that calculates a normalized value used for theload-balancing process, based on address information included in thepacket. Additionally, the node apparatus corresponding to the ingressnode has a switching-information creating unit that adds the normalizedvalue to switching information of the packet. Therefore, the nodeapparatus corresponding to the ingress node can notifies an areaboundary node about the normalized value.

[0130] Additionally, a node apparatus corresponding to an area boundarynode located on a boundary of areas has a normalized-value extractingunit that extracts the normalized value used for carrying out theload-balancing process within an area including the area boundary node,from the switching information of the packet supplied from an adjacentarea. Consequently, the area boundary node can carry out theload-balancing process by use of the normalized value, and does not needto identify a protocol or to check a header of the protocol.Accordingly, the area boundary node can carry out the high-speedload-balancing process.

[0131] A node apparatus in an area has a failure notifying unit thatnotifies the closest load-balancing node on the upstream side in thearea about the failure if detecting the failure. Thus, theload-balancing node can distribute the traffic flowing through a failedpath speedily.

[0132] The ingress node or the area boundary node has a trafficdistributing unit that redistributes the traffic flowing through thefailed path, to paths other than the failed path, thereby relieving thetraffic loss of the traffic flowing through the failed path speedily.

[0133] Additionally, the ingress node or the area boundary node has afailure-notification receiving unit deciding whether the traffic lossoccurs by redistributing the traffic flowing through the failed path, tothe paths other than the failed path, and, thus, the ingress node or thearea boundary node can recognize whether the traffic flowing through thefailed path can be redistributed to the paths other than the failedpath.

[0134] If the failure-notification receiving unit decides that thetraffic loss occurs by redistributing the traffic flowing through thefailed path, to the paths other than the failed path, the trafficdistributing unit switches the traffic flowing through the failed path,to a newly set path. Thus, the traffic distributing unit can relieve thetraffic flowing through the failed path, even if the paths other thanthe failed path have high traffic.

[0135] The above description is provided in order to enable any personskilled in the art to make and use the invention and sets forth the bestmode contemplated by the inventors of carrying out the invention.

[0136] The present invention is not limited to the specially disclosedembodiments and variations, and modifications may be made withoutdeparting from the scope and spirit of the invention.

[0137] The present application is based on Japanese Priority ApplicationNo. 2000-389077, filed on Dec. 21, 2000, the entire contents of whichare hereby incorporated by reference.

What is claimed is:
 1. A traffic engineering method of a network dividedinto a plurality of areas, each area including a plurality of nodes,said method comprising the step of carrying out a load-balancing processin said each area separately.
 2. The traffic engineering method asclaimed in claim 1, further comprising the step of deciding adestination of a packet in said each area.
 3. The traffic engineeringmethod as claimed in claim 1, further comprising the steps of:calculating a normalized value used for the load-balancing process,based on address information of the packet supplied to an ingress nodeof the network from an outside of the network; adding said normalizedvalue to switching information of said packet; and forwarding saidpacket from said ingress node to the plurality of nodes.
 4. The trafficengineering method as claimed in claim 3, further comprising the stepsof: receiving said packet from said ingress node at an area boundarynode located on a boundary of the plurality of areas; and extractingsaid normalized value used for carrying out the load-balancing processin an area including said area boundary node, from the switchinginformation of said packet.
 5. The traffic engineering method as claimedin claim 1, further comprising the step of notifying a closest nodeapparatus that carries out the load-balancing process and is the closestto said node apparatus on an upstream side of said node apparatus, abouta failure if detecting the failure.
 6. The traffic engineering method asclaimed in claim 4, further comprising the step of redistributing atraffic flow from a failed route to a route other than the failed routeif receiving a failure notification at said ingress node or said areaboundary node.
 7. The traffic engineering method as claimed in claim 6,further comprising the step of deciding whether a traffic loss occurs byredistributing the traffic flow from said failed route to the routeother than said failed route if receiving the failure notification atsaid ingress node or said area boundary node.
 8. The traffic engineeringmethod as claimed in claim 7, further comprising the steps of: setting anew route, if said failure-notification receiving unit decides that thetraffic loss occurs by redistributing the traffic flow from said failedroute to the route other than said failed route; and switching thetraffic flow from said failed route to the new route.
 9. A nodeapparatus included in a network that is divided into a plurality ofareas, each area including a plurality of nodes, in which an entirenetwork resource is optimized by traffic engineering, said nodeapparatus comprising an inside-area destination deciding unit thatdecides a destination of a packet in said each area, said destinationbeing used for carrying out a load-balancing process within said eacharea.
 10. The node apparatus as claimed in claim 9, wherein said nodeapparatus corresponding to an ingress node supplied with the packet froman outside of the network includes a normalized-value calculating unitthat calculates a normalized value used for the load-balancing processbased on address information of said packet, and a switching-informationcreating unit that adds said normalized value to switching informationof said packet.
 11. The node apparatus as claimed in claim 9, whereinsaid node apparatus corresponding to an area boundary node located on aboundary of the plurality of areas includes a normalized-valueextracting unit, which extracts a normalized value used for carrying outthe load-balancing process in an area including said node apparatus,from switching information of the packet supplied from an adjacent area.12. The node apparatus as claimed in claim 9, further comprising afailure notifying unit that notifies a closest node apparatus thatcarries out the load-balancing process and is the closest to said nodeapparatus on an upstream side of said node apparatus, about a failure ifdetecting said failure.
 13. The node apparatus as claimed in claim 10,further comprising a traffic distributing unit that redistributes atraffic flow from a failed route to a route other than the failed routeif receiving a failure notification.
 14. The node apparatus as claimedin claim 13, further comprising a failure-notification receiving unitthat decides whether a traffic loss occurs by redistributing the trafficflow from said failed route to the route other than said failed route ifreceiving the failure notification.
 15. The node apparatus as claimed inclaim 14, wherein said traffic distributing unit switches the trafficflow from said failed route to a newly set route, if saidfailure-notification receiving unit decides that the traffic loss occursby redistributing the traffic flow from said failed route to the routeother than said failed route.
 16. The node apparatus as claimed in claim11, further comprising a traffic distributing unit that redistributes atraffic flow from a failed route to a route other than the failed routeif receiving a failure notification.
 17. The node apparatus as claimedin claim 16, further comprising a failure-notification receiving unitthat decides whether a traffic loss occurs by redistributing the trafficflow from said failed route to the route other than said failed route ifreceiving the failure notification.
 18. The node apparatus as claimed inclaim 17, wherein said traffic distributing unit switches the trafficflow from said failed route to a newly set route, if saidfailure-notification receiving unit decides that the traffic loss occursby redistributing the traffic flow from said failed route to the routeother than said failed route.
 19. A network system, comprising aplurality of areas, each area including a plurality of nodes, wherein anentire network resource is optimized by traffic engineering, and aload-balancing process is carried out in said each area separately.